/*
* Copyright (C) 2022 Huawei Device Co., Ltd.
* Licensed under the BSD License, (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
*     https://opensource.org/licenses/BSD-3-Clause
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/

import { BaseMatcher } from '../BaseMatcher';
import { Description } from '../Description';
import { Matcher } from '../Matcher';
import { IsNot } from './IsNot';

/**
 * Is the value null?
 */
export class IsNull<T> extends BaseMatcher<T> {
  public matches(o: Object): boolean {
    return o == null;
  }

  public describeTo(description: Description): void{
    description.appendText("null");
  }

  /**
   * Creates a matcher that matches if examined object is <code>null</code>.
   * For example:
   * <pre>assertThat(cheese, is(nullValue())</pre>
   *
   * @return The matcher.
   */
  public static nullValue(): Matcher<Object>{
    return new IsNull<Object>();
  }

  /**
   * A shortcut to the frequently used <code>not(nullValue())</code>.
   * For example:
   * <pre>assertThat(cheese, is(notNullValue()))</pre>
   * instead of:
   * <pre>assertThat(cheese, is(not(nullValue())))</pre>
   *
   * @return The matcher.
   */
  public static notNullValue(): Matcher<Object> {
    return IsNot.not(IsNull.nullValue());
  }
}
